1. Field of the Invention
The present invention relates generally to a wheel driver, and more particularly, to a wheel driver in a portable electronic device.
2. Description of the Related Art
A jog wheel allows a user to reproduce audio or video content. Recently, jog wheels have been employed as interfaces for menu selection on portable terminals, such as portable phones, music players, or Personal Digital Assistants (PDAs). For example, jog wheels are used for scrolling menu entries on a portable terminal, or for controlling the movement of a mouse pointer displayed on the portable terminal.
Typically, jog wheels have been implemented with electrical capacitive sensing or magnetic sensing. In such cases, it is necessary to provide one or more sensors (e.g., hall sensors) for sensing an electrical capacitive circuit or magnetic field around the jog wheel. Consequently, if such a jog wheel is applied to a portable terminal, the size (or thickness) of the portable terminal would increase.
Korean Patent Publication No. 10-2008-0039814 entitled “User Navigation Device and Method of Producing the Same” has proposed a jog wheel which attempts to solve the problem of resulting increased portable terminal size. FIG. 1 illustrates a circuit of an optical reflective jog wheel, and FIG. 2 illustrates a code wheel provided in the circuit of FIG. 1. The optical jog wheel 100, shown in FIG. 1, includes a turn dial 102, a pattern wheel 104, an encoder 106, a decoder 108, and a microprocessor 110. The turn dial 102 is physically coupled to the pattern wheel 104. If a user manually rotates the turn dial 102, the pattern wheel 104 is rotated. As shown in FIG. 2, reflective sections 144 and non-reflective sections 142, which are the same in width, are alternately and repeatedly provided on the pattern wheel 104.
The encoder 106 includes an emitter 120 and a detector 130. The emitter 120 includes a light source 122, such as a Light Emitting Diode (LED), and the detector 130 includes one or more optical detectors 132, such as a photodiode. Signals produced by the photodiodes 132 are processed by a signal processing circuit 134 for producing channel signals CHA and CHB.
FIG. 3A illustrates signals produced by the photodiodes 132 when the code wheel rotates counterclockwise, and FIG. 3B illustrates signals produced by the photodiodes when the code wheel rotates clockwise. Referring to FIGS. 3A and 3B, a first photodiode inputs a reference signal for confirming direction, and a second photodiode inputs a signal at a different timing. The signal input by the second photodiode is input differently depending on the rotating direction of the code wheel. The signal processing circuit 134 determines the rotating direction of the pattern wheel 104 by confirming the timing of the signal input by the second photodiode with reference to the signal input through the first photodiode.
Consequently, the above-described conventional optical reflective jog wheel requires at least two photodiodes. In addition, its response time is poor because the rotating direction of the pattern wheel 104 is determined after the signals input through the two photodiodes are confirmed.